This invention pertains to the art of removing cut out profiles of vinyl, plastic or other material. The invention is particularly useful in a system where layers of material are sealed using radio frequency, thermal or ultrasonic sealing, however it is not limited to these materials or sealing.
For example, in a radio frequency (RF) sealing system, sealing occurs by the joining of thermal plastic film or sheet materials with heat that is produced by radio frequency energy. This heating is typically done in a press containing an electrode (die) that is shaped to the configuration desired in the finished product. As in other molding processes, the variables are heat, pressure, and time. Heat is produced by the reaction of the plastic to the high frequency energy from the RF generator. The amount of heat is proportional to the amount of RF power applied and the heatability of the plastic. Often a heated platen is used to stabilize the temperature. The pressure is typically supplied by a pneumatic system and is varied by changing the air pressure in the pneumatic: system. Time is controlled by electric timer built into the machine.
Typical machines include a pre-seal timer to allow full pressure of the electrode against the material before the RF power is applied. A heat or seal timer controls the length of the RF power cycle. A dwell or cool timer is used to allow the material to cool and set while pressure is still applied.
In the RF sealing process, shown in FIG. 5a, the sealing bar and the ground are separated by a buffer (FIG. 5b), both of which are electrically conducting. The press is electrically connected to the ground of the RF frequency generator. The RF signal is applied between the sealing bar and the ground. It is seen then that a requirement is that the sealing bar and ground be electrically separated else a short is created and the system fails. A buffer is used to enhance the RF sealing process preventing loss of heat, requiring less power, helping to prevent; arcing due to over sealing, concentrating heat and eliminates the sticking of materials.
In a system where the sealing bar seals two or more materials together in a contiguous seal, and where profile created by seal, is to be punched out, it is necessary in the prior art to first seal the materials using the RF method, then in a later step in the process punch the hole using the typical hole punch and in a still final step, remove the insert (sometimes referred to as a "cut out", "hole", "dot", or "profile"). Some unconventional systems use vacuum removal but because of the size of the vacuum needed, and because of the nature of a punching system having a plurality of holes allowing for vacuum leaks, such a system is often impractical and uneconomical.
Consequently, it is an object of this invention to remove profiles cleanly and economically. It is further an object to combine the sealing, punching, and profile removing steps into the production line of the aforementioned sealing processes, and to do so economically, and in an RF system to do so without arcing.
To do so during the process requires that the punch fit inside the sealing electrode die. However the resulting gap can still be problematic in that air gap arcing often occurs effectively shorting the RF circuit resulting in a lack of sealing and other problems.
One method used is to allow the profiles to build up inside the receiving RF sealing cylinder, which cylinder directs the profile to a hole in the side of the cylinder for the profiles to eventually fall out; however in such a system, the profiles don't always fall out and will sometimes jam up. Moreover, the profiles that do fall out the side fall onto the material and work surface area.
The invention is directed primarily to achieving these objectives in a system utilizing a plurality of hole punches in an RF sealing process so as to punch at one time a plurality of holes at the time the RF sealing die is still pressed against the materials. The invention apparatus in one form is comprised of a die being the RF electrode, which die has therein a plurality of cylinders for receiving the base punches. The cylinders are connected to a plenum having both an air jet to create high speed airflow over the hole, and a vacuum so as to remove the profiles upon punching following the RF sealing. During the RF sealing process, a thin moving secondary disposable buffer is introduced, not static, to fine tune an existing buffer system, such as a reusable thicker buffer. The buffer is comprised of a dielectric or other insulating material, usually paper, so as to block the punch/electrode gap and prevent the arcing that otherwise might occur.
Other objects and features of the invention and the manner in which the invention achieves its purpose will be appreciated from the foregoing and the following description and the accompanying drawings which exemplify the invention, it being understood that changes may be made in the specific method and apparatus disclosed herein without departing from the essentials of the invention set forth in the appended claims.